280 



[November, 



CRETACEOUS SPECIES. 



Gen. CALLIANASSA. 



0. DANAi, Hall & Meek, Mem. Am. Ac. Arts & Sc. Bost. vol. 5, n. s. p. 319 



Gen. BELEMNITELLA. D'Orbigny. 



Formations in 

 ascending order. 



1|B. MUCRONATA * Schlotheim, sp. Petfr. p. 47, No. 4 



B ? BULBOSA, Meek and Haydeu, Proc. Acad. Nat. Sc. Phila. vol. 8, p. TO 



Gen. NAUTILUS. 

 1|N. Dekayi, Morton, Synopsis Org. Rem. p. 33 



Gen. AMMONITES 



II A. PLACENTA, Dekay, Ann. N. Y. Lye. Nat. Hist. vol. 2, p. 5, fig. 2 (not. 3) 



II A. LOBATUs,t Tuomy, Proc. Acad. Nat. Sc. Phila. vol. Y, p. 168 



A. lenikularis, Owen, Rept. Iowa, Wisconsin and Min. tab. 8, fig. 5 



A. OPALis, Owen, " " " " " 6 



A. COMPLEXUS, Hall and Meek, Mem. Am. Ac. Arts & Sc. vol. 5, n. s. p. 394 

 A. PERCARiNATUS, Hall and Meek, " " " " " 396 



A. Halli, Meek and Hayden, Proc. Acad. Nat. Sc. Phila. vol. 8, p. TO.... 



Gen. TURRILITES. 



T. NebrascensisJ 



Aneyloceras ? Nebrascensis, Meek and Hayden, Proc. Ac. Nat. Sc. Phila 



vol. 8, p. 71 



T. Cheyennensis 



Aneyloceras ? Cheyenensis, Meek and Hayden, Proc. Ac. Nat. Sc. Phila. 

 vol. 8, p. tl 



*? 



*? 



*? 



Note. This mark (|| ) indicates that the species is also known to occur in the States ; 

 this () that it is common to this country and the old world ; and these two (||) that 

 it occurs both in the States and on the other side of the Atlantic. 



* "We place this species in the list of Nebraska Fossils, on the authority of Dr. Morton, 

 (see Belemnites mucronatus, Jour. Acad. Nat. Sc. vol. 8, p. 211) not having recognized it 

 in any of the collections we have seen from that region. 



f Adult specimens of this shell almost equal in size the largest individuals of A- 

 placenta, with which species it is apt to be confounded. They may always be distin- 

 guished, however, by external characters, even when the septa cannot be seen ; the 

 dorsal margin of the former being thin and sharp, especially in young individuals, 

 while that of A. placenta is always flattened immediately on the edge. It is a little 

 remarkable that Dr. Dekay's original description agrees more nearly with this shell 

 than with that referred by Morton and others to A. placenta, while his figure is more 

 like the latter. Possibly he may have had fragments of both species before him. 



Suspecting our Nebraska shell might be identical with a species indicated by Prof. 

 Tuomy, from Mississippi, under the name of A. lobatus, we sent him drawings of one of 

 our specimens, showing its form and all the details of the septa, since which he writes 

 he has no doubt of their identity. As the name lenticularis was previously applied to 

 one or two other species, that given this shell by Prof. Tuomy will have to take pre- 

 cedence, though published after Dr. Owen's. 



f Having at first only unsatisfactory fragments of this and the following species, we 

 were much puzzled in regard to their afiinities, and referred them provisionally to the 

 genus Aneyloceras. Better specimens recently received, prove them to be Turrilites. 



